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Post by Dillzio on Aug 20, 2009 9:17:09 GMT 1
Hi all, Having burnt out an ESC myself, and hearing numerous stories about the same, I have created this thread to pay homage to the stock electronic speed controller that has caused so many of us so much lost flight time. I pulled apart my burnt out ESC, it turns out that the burnt out component is the power transistor. Writing on it is: T430 BB7RBV I tried looking up the specs, couldn't find anything. Was chatting to some people in another thread ( supercubclub.proboards.com/index.cgi?board=batt&action=display&thread=2455&page=1 ) and one of the ducks (lol) suggested adding a heatsink to the transistor. I did a bit of reading up on heatsinks at www.kpsec.freeuk.com/components/heatsink.htm ...it says there that "power transistors used in circuits such as an audio amplifier or a motor speed controller will be partly on most of the time and VCE may be about half the supply voltage. These power transistors will almost certainly need a heat sink to prevent them overheating" Guess what isn't on the power transistor in the stock super cub? YOU GUESSED IT, NO HEATSINK! They may be talking about applications where the transistor controls the output voltage to the motor, rather than just cutting in and out 1000 times a second like a modern ESC. Still though, the transistors are clearly burning out under load, and adding a heatsink can only be an improvement. So, I'll definitely be attaching one to my new receiver (when it FINALLY arrives, my local distributor is still waiting on their first shipment of spare parts for the LP from overseas). If I can find a tiny 5V fan that draws low amps i might be able to attach that to a power line from a servo too. If we can use our collective genius to come up with a simple mod to increase the longevity of the stock ESC I think it will save a lot of people a lot of time and money. Here are the pics of my toasted ESC. You can see the melted plastic just above the LiPo jumper  You can see the scorch marks on the power transistor. It got so hot the soldier on the pins melted and disconnected the transistor from the board.  Here is a close up of the transistor (just in front of the power wires). I bent it so that it would stand up.  |
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Post by Dillzio on Aug 23, 2009 8:28:24 GMT 1
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Post by flydiver on Aug 23, 2009 16:42:00 GMT 1
There seems to be an inordinately high failure rate in the new LP Cub RX/ESC. I think they did a redesign for the lipo and it appears they got some poor electronics, poor QA, or maybe a faulty design.
FWIW there is a LOT more wrong with that unit's design than the transistor. For example, the little solder joints where the servo plug is soldered to the board tends to crack and make the controls go crazy. Folks figure it's a 'glitch' and run out and buy Spectrum. I have a posting on that issue. It's happened to me on 2 out of 4 units, a pretty poor showing.
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Post by duck9191 on Aug 23, 2009 22:44:20 GMT 1
the metal on the back of the fet is a heatsink, just not a very big one. one important thing about adding a heatsink is to make sue none of the pins touch the heatsink compound or the heats sink its self, or it will short.
like fly said, there is alot more wrong with the esc then just the underpowered fet, poorsolder work, poor thorttle proportioning and many other issues.
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Post by flydiver on Aug 24, 2009 0:36:18 GMT 1
poor thorttle proportioning I checked that. There are 5 discrete throttle positions in the stock unit. That's pretty crude. OTOH, for the stock Cub not much more is needed. I'd let HZ know of this issue. They'll claim they know nothing at all about chronic problems like this. That's BS, they do. They monitor them pretty closely. They generally do have pretty good customer service so if you make a convincing case for a failure due to THEIR issues they'll generally make good on it. |
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Post by Dillzio on Aug 25, 2009 6:32:35 GMT 1
poor thorttle proportioning I checked that. There are 5 discrete throttle positions in the stock unit. That's pretty crude. Are you sure that's the case with the new receiver/ESC from the LP? When mine was working (seems like a distant memory now) throttle response seemed to be really smooth. |
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Post by Dillzio on Oct 14, 2009 12:29:01 GMT 1
Now that I have mine going again, I ran it to see how hot that power transistor gets during normal operation. It gets hot enough to burn within 20 seconds of WOT. I'll be adding the heatsink as soon as I can get my hands on a rotary-tool.
It sure is a glitchy radio though, and today I realized one of the stupidest things ever - in their neutral positions, the elevator and rudder move when you flip the dual-rate switch on or off (I have ACT disconnected). I could imagine that it might want to give a little up elevator with ACT on, but moving the rudder makes NO sense whatsoever.
In my haste to get my hands on a replacement ASAP, I now have one replacement and still have another two on the way! Looks like I can probably afford to burn out a couple more ESCs ;D
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Post by killioughtta on Oct 14, 2009 14:29:10 GMT 1
Or you can get some servos and motors and build airboats
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Post by Dillzio on Oct 14, 2009 15:30:03 GMT 1
Or you can get some servos and motors and build airboats Well, now that you mention it, I do happen to have spare servos, motor and gearbox too. An airboat eh? |
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Post by killioughtta on Oct 14, 2009 17:24:27 GMT 1
An Airboat! Like mine ^_^   |
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Post by Dillzio on Oct 19, 2009 3:00:07 GMT 1
Heat sink has been trimmed to fit and glued in place. Glue is setting now, just have to wait and see if the case will still fit without me having to cut a hole in it.  |
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Post by Dillzio on Oct 19, 2009 7:07:51 GMT 1
I've just realised that the stuff I bought was a heat-sink heat-transfer paste, not a glue. I was under the impression that you can get heat sink paste with copper in it that acts as an adhesive too, but I couldn't be bothered chasing it up. I decided to use super glue instead, the thin runny stuff. When joining two perfectly flat surfaces that sort of superglue has them practically touching each other, so the heat transfer capability should be there. I just tested it by running my motor WOT for about 10 minutes, and it worked beautifully. The heat sink does get warm, but no where near as hot as the back of the transistor was getting. I can still touch the metal transistor underneath too and it never got hot enough to burn. Also, it didn't get hot enough to melt the super glue either, the hold wouldn't budge! I've trimmed the case to make room for the heat sink, and now it fits beautifully:   |
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Post by duck9191 on Oct 20, 2009 1:53:47 GMT 1
what you needed was thermal epoxy, but for this application the CA should work fine. that thing should help alot with over heating.
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Post by flydiver on Oct 20, 2009 2:09:29 GMT 1
Depending on how the surfaces line up you can sometimes cover the main contact body with thermal paste and then put CA on the edges to bond it down. Might not work well for this area since it's such a small contact surface.
I find it interesting that the FETs on a 'normal' ESC are the surfaces that heat up. Most manufacturers provide and aluminum heatsink. Then they cover the whole mess with shrinkwrap which probably is rotten for heat dissipation.
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Post by hbullis on Jul 12, 2011 17:24:41 GMT 1
Ha! I just found this site looking for the same replacement transistor. I just took one out of the brand new reciever I got from Hobby Zone (not related to the mfg of the Super Cub).
I bought a new reciever and a new motor since they burnt up at the same time. Plus new wing, tail etc. that was tore up when it stuck in on an island surrounded by alligators.... no kidding here! I had to retrieve it with a tree trimmer pole! I live on a lake in FL.
The one Hobby Zone sent didn't work out of the box!. Each time I went to full power the engine would cut off. Three quarter throttle was all I could get. Also the control surfaces would not null and stay put. Constantly moved and the motor also would come on by itself.
I opend the new reciever. Total re-design it appears. So I took out the output transistor (T430) to place in the old burnt up unit. Not done that yet. Copper traces are vaporized!
Has anyone had this problem or know if the circuit was redesigned? Maybe they sent the wrong thing...looks identical outside though.
I do want to say neither Hobbyzone.com or Horizon Hobby was any real help. I wrote 1-1/2 pages with pics and told them the new reciever was also defective also. They said send it in takes 2 weeks to repair.......thanks but no thanks.
Heat sink is an excellent idea. I do want to mention many transistors operate at temps safely at higher temps than you can place your finger on even for a second (I worked many years in E's R&D electronics group by the way).So the finger idea is not accurate. I have a IR gun for my nitro cars though. May check that temp.
Ok done rambling! Nice site!
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